The present invention relates generally to rotary milling cutters and is more specifically concerned with a new and improved arrangement for locking cutting inserts on a cutter body.
Insert type milling cutters have achieved considerable popularity in the metal working field. Typically the inserts are made of a very hard cutting material such as tungsten carbide. A milling cutter and insert construction which has greatly enhanced the metal removing capability of insert type cutters is disclosed in the commonly assigned U.S. Pat. No. 3,574,911, dated Apr. 13, 1971. In that patent are disclosed tungsten carbide inserts having sinusoidal serrations forming the cutting edges. The inserts are arranged at locations around the circumference of the cutter body with the sinusoidal cutting edges of each insert being phased relative to those of the other inserts so that the milling cutter accomplishes a phased cutting action.
It has been observed that phased sinusoidal cutting inserts may, in certain situations, create drag on a workpiece being machined which may be greater than that of other types of milling cutters, such as plainsided inserts. For example, it has been observed in certain instances that the serrated sinusoidal cutting edges drag in the serrated sinusoidal form left on the sidewall of the workpiece being machined. The resultant forces which are generated by such dragging attempt to dislodge the insert from its seat on the cutter body. If an insert is moved or dislodged from its correct position, the phased cutting action of this type milling cutter is impaired. Once the phasing is interrupted, the problem is compounded. The dragging effect increases with the result that other inserts in the cutter body will be more likely to line themselves up with the phase of the preceeding insert thereby impairing the effectiveness of cutting action. Attention to cutter geometries can alleviate the problem, but may not eliminate it for all cutting conditions. While the aforementioned patent discloses inserts having triangular shapes, it will be appreciated that other insert shapes may be used in phased multi-insert cutters; for example, a rectangular shaped insert is a known type of insert.
Hence, when sinusoidal cutting inserts are used, care must be taken to mount them in such a way as to maintain them in the desired locations on the cutter body in spite of the increased drag forces which may be applied to them tending to move or to dislodge them from their seats on the cutter body.
The present invention is directed to a new and improved mounting arrangement for mounting cutting inserts on the body of a milling cutter. With the invention, a more secure mounting of cutting inserts on a cutter body is achieved. This allows the inserts to withstand drag forces to which they may be subjected when in use, without being shifted in or dislodged from their seats. A particular advantage of the invention is that movement of an insert axially along the direction of its cutting edge is eliminated. This is especially important in phased multi-insert cutters, for it means that the phasing action will not be impaired due to movement of the inserts axially on the cutter body. Not only is an improved mounting achieved with the invention, but also the inserts may be expediently removed and installed when it is desired to change the cutting edges. Still another advantage of the invention is that it takes up a relatively small amount of space and hence allows very close spacing between inserts on a cutter body. The invention also allows a variety of different shaped inserts to be mechanically held on a cutter body. While the invention is especially beneficial for phased sinusoidal insert cutters, its principles may be used with other types of inserts. Still another advantage of the invention is that the inherent strength of the cutter body is not significantly impaired when the insert mounting arrangement is incorporated.
Briefly, the invention provides a mounting arrangement for milling cutter inserts wherein a pair of axially spaced grooves are provided in an exposed surface of the insert. A pair of threaded holes are provided in the cutter body adjacent to the grooves. A fastener is threaded into each threaded hole and advanced so that the circular edge of the head of the fastener engages the corresponding groove in a wedging manner. The insert is thereby locked in the seat very securely, and the possibility of axial movement is virtually eliminated when the cutter is put to use. The axis of each fastener is disposed in the same plane as and at an acute angle to the axis of the corresponding groove. Each groove has an elliptical transverse cross section corresponding to the elliptical projection of the corresponding fastener head when viewed axially of the groove.
The foregoing features, advantages and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings.
The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time for carrying out the invention.